Add IsMainThread to nsIThread. r=danm@netscape.com, sr=darin@netscape.com 112397

xpcom/threads/nsIThread.idl

@@ -121,6 +121,8 @@ interface nsIThread : nsISupports
 
     // return the "main" thread
     static NS_COM nsresult GetMainThread(nsIThread **result);
+
+    static NS_COM PRBool IsMainThread(); 
 %}
 };
 

xpcom/threads/nsThread.cpp

@@ -415,6 +415,17 @@ nsIThread::GetMainThread(nsIThread **result)
     return NS_OK;
 }
 
+NS_COM PRBool
+nsIThread::IsMainThread()
+{
+    if (gMainThread == 0)
+        return PR_TRUE;
+    
+    PRThread *theMainThread;
+    gMainThread->GetPRThread(&theMainThread);
+    return theMainThread == PR_CurrentThread();
+}
+
 void 
 nsThread::Shutdown()
 {